The present invention relates to tackified adhesive compositions, particularly to such compositions tackified with a phenol-diene-olefin resinous reaction product.
It has been the general practice in the manufacture of adhesives from elastomeric materials, such as natural rubber, polyisoprene, cis-polybutadiene, styrene-butadiene rubbers, ethylene-propylene rubbers, and the like, to mix with the elastomers, a tackifying agent sometimes merely called a tackifier. The tackifying agent is added to the elastomer to enable the normally weakly tacky or non-tacky elastomers to become tacky, i.e., to be capable of adhering to a surface with the application of very little or no pressure.
For the most part, the tackifiers for elastomers are rosin, modified rosins, polyterpene resins and coumarone-indene resins. Other resins of importance are the reaction products of alkylphenols with acetylene and the reaction products of phenols with aldehydes.
Of particular importance in the manufacture of adhesives from natural and synthetic rubbers has been the terpene resins. The resins prepared from .beta.-pinene have been especially important in the manufacture of adhesives. The use of .beta.-pinene in the manufacture of tackifiers for adhesives, however, has become restricted because of its limited supply and because of the growing use of .beta.-pinene in other fields. Terpenes therefore have been extended for use as tackifiers by reaction with phenols.
U.S. Pat. No. 3,383,362 discloses reacting phenols with cyclic polyolefin and terpene, sesquiterpene, dihydroterpene or a low molecular weight propylene polymer to produce tackifiers. Such tackifiers, however, require large amounts of the expensive terpenes. Tackifiers from rosin, modified rosins, coumarone-indene resins and phenol condensation products with acetylene and aldehydes, furthermore have not adequately provided replacement for polyterpene resins because they have a variety of deficiencies. For example, some fail to produce a sufficiently high degree of tack, others are too expensive, and still others are chemically unstable.
Low molecular weight reaction products of phenols and dienes are known but not in forms which are suited for use as tackifiers. U.S. Pat. No. 3,336,398, for example, discloses the reaction of phenols with a diene, i.e., dicyclopentadiene, at temperatures which converts the dicyclopentadiene to a conjugated cyclodiene, producing a product having ethylenic unsaturation. Such unsaturated materials are not chemically stable.
U.S. Pat. No. 2,471,454 teaches dihydroterpene-substituted phenol compounds rather than diene-substituted phenols, requiring expensive terpenes as a starting material. U.S. Pat. No. 2,864,868 discloses the reaction product of conjugated dienes with phenols to produce hard, dark resinous products having blocks of polymerized diene and also having ethylenic unsaturation. As well as being chemically unstable, such products are not compatible with some elastomers.